This disclosure concerns the formation of fluorescent metal nanoparticles (NPs) within nanocapsules catalyzed by high-energy gamma radiation. The nanocapsules are based on block co- or terpolymers, and contain an aqueous phase.
The NP formation is a means of indicating that the catalyst (the radiation) was once present.
In one embodiment, we have used gamma ray-initiated reduction of silver ions in the encapsulated aqueous solution to form silver atoms, which then aggregate to form the fluorescent NPs.
In an end application, the nanocapsules can be suspended in a transparent resin that can be applied to walls, floors, etc. and allowed to dry.
Periodic testing for NP fluorescence will reveal if gamma radiation (thus, possibly weapons of mass destruction) was present in the vicinity.
We have found that use of the proper block copolymer as nanocapsule material leads to gamma-ray initiated formation of nanoparticles that have a distinctive fluorescence spectra. These spectra are quantitatively different from those arising from nanoparticles that are formed in other types of nanocapsules, or formed using other reactants such as reducing agents or UV irradiation.
This distinction is crucial for the effective use of the NPs as detectors of gamma radiation from fissile materials. This discovery of novel nanomaterials that interact with or are formed by high energy radiation provides a foundation for new nanoscale radiation indicators.
These discoveries are expected to have a large interest, because many types of fissile material (enriched uranium, for example) emit gamma radiation. The nanocapsules can be embedded in transparent resins that can be painted onto surfaces that may be exposed to fissile materials. Examples of such surfaces are the insides of shipping containers, truck, ship, or aircraft cargo compartments, and interior walls of storage depots.